#1: you can't find information. Now that might just be that you suck at doing research of course, but lets assume there just isn't any to be found. How strange!
#2: but is it really strange? Its called web start

Using webstart you want to boot things through the web. It just doesn't make any sense to want to store stuff on an FTP server (which you would publicly have to open up to the entire world) or to expect support for that to be built in. The fact that most web browsers can do simple FTP stuff is a convenience provided by those browsers only.